The original question is asking us to compare the total occurrence of both x and o character but I have modified it so we can compare any two characters as we wish to. We also need to make sure we can compare the total occurrence of those characters regardless of lower or uppercase character.

You need to find what is the position of each character in a string from a character list and then return the entire character positions in a single string with space between each character position excepts the last one. You need to ignore all those characters that are not in the character list which is consists of character a-z.